1. Field of the Invention
The present invention relates to a light deflector manufactured by applying a semiconductor manufacturing process technique.
2. Description of the Related Art
Recently, attention has been directed to a light deflector manufactured by applying a semiconductor manufacturing process technique, i.e., a light deflector manufactured by applying MEMS technology. A light deflector that oscillates at a resonant frequency is disclosed in, for example, U.S. 2002/118429.
This light deflector comprises a movable plate having a reflective surface, a pair of torsion bars supporting the movable plate so as to allow it to oscillate, and a supporting member holding the torsion bars. The movable plate has a first portion having the reflective surface, and a second portion having electric elements that constitute part of actuating means to actuate a mirror oscillating member. The first portion has a reflective surface forming surface in which the reflective surface is formed, and the second portion has an electric element forming surface in which the electric elements are-formed. The reflective surface forming surface is smaller than the electric element forming surface, and has a shape such as an elliptic shape substantially inscribed in a rectangle of the electric element forming surface. An electromagnetically actuating method is employed, and the electric element is a drive coil going around the edge of the movable plate. This drive coil is disposed in a space having magnetic flux perpendicular to an oscillation axis, and oscillates the movable plate by a Lorentz force caused by passing an electric current through the drive coil.
In this light deflector, the area of the second portion is made smaller than that of the first portion configuring the movable plate so that the moment of inertia of the movable plate is reduced while the size of the movable plate and the dynamic flatness of the movable plate are maintained. As a result, the stiffness of the torsion bar can be reduced while maintaining a constant resonant frequency, thereby allowing actuating efficiency to be improved. Thus, the overall actuating efficiency is improved while maintaining the resonant frequency and mirror performance.
In a present application using a light deflector, a light deflector that manages both high-speed scanning and low-speed scanning is desired. More specifically, a light deflector is desired that can change an actuating frequency within a predetermined region in the low-speed scanning and that can actuate at a constant frequency higher than a low-speed scanning region in the high-speed scanning. It is naturally preferable that the low-speed scanning region may be wide and that the difference between the high speed and the low speed may be large.